1. Field Of Invention
This invention relates to the measurement of motorcycle and ATV (All Terrain Vehicle) suspension system deflections in various loaded and unloaded positions.
2. Description Of Prior Art
It is important that the deflection of a motorcycle or ATV suspension system be measurable by the rider with a fair degree of accuracy. This is especially significant for off-road vehicles used on all types of terrain and for racing motorcycles or ATV's on prepared tracks.
The method commonly used to measure these deflections involves the use of a tape measure, the rider, and the cooperation of two assistants. Up to the present the procedure has been as follows:
(1) With the motorcycle or ATV supported on a workstand and the rear wheel completely off the ground, measure the distance between the rear fender mounting bolt and the center of the rear axle using a tape measure. This is the reference measurement with the suspension system completely unloaded.
(2) The motorcycle is now removed from the workstand and the rider mounts the vehicle placing his feet on the pegs. This deflects the motorcycle suspension system to the fully loaded position. During this procedure number one assistant must steady the vehicle to prevent it from falling sideways.
(3) In this fully loaded position number two assistant now measures the distance between the rear fender mounting bolt and the center of the rear axle, using the same tape measure.
(4) The fully loaded measurement taken in step 3 must now be subtracted from the unloaded measurement taken in step 1. This difference in deflection is commonly referred to as the race sag.
(5) The motorcycle or ATV is now held upright in the normal position with the rear wheel resting on the ground, without the rider's weight. The rider or one of his assistants now measures the distance between the rear fender mounting bolt and the center of the rear axle.
(6) The measurement taken in step 5 must now be subtracted from the measurement taken in step 1 to determine the sag due to the weight of the sprung portion of the motorcycle or ATV alone.
The above measurement procedure utilizing the rider and two assistants is clumsy, time consuming, prone to miscalculation, and subject to inaccuracies in measurement.
All owners manuals and competition handbooks recommend this method of suspension measurement as is evident from the 1990 Honda CR250R owners manual and competition handbook.